Simon Bolivar had spent fourteen years fighting Spain. By the summer of 1824 he had liberated New Granada, Venezuela, and Quito. Peru had declared independence in July 1821, but the royalists had clawed back control of Lima the previous February, and Bolivar regrouped in Trujillo before marching south. He had about eight thousand soldiers, with one thousand cavalry. Field Marshal Jose de Canterac commanded the Spanish forces in the central Peruvian highlands - also about eight thousand troops, with thirteen hundred cavalry, the seasoned core of an army that had held Peru for two and a half centuries. The two armies converged on the high pampa west of Lake Junin in early August. Bolivar moved first, sending his cavalry forward to delay Canterac's withdrawal toward Cusco. Canterac sent his cavalry forward to disrupt Bolivar's. The infantry of both armies was still hours behind.

The Spanish cavalry reached the patriots first and caught them unprepared. The shock charge struck the squadron of Colombian Grenadiers under General Necochea, including Major Otto Felipe Braun, a German-born cavalry officer who had joined the South American liberation movement. The Grenadiers held briefly and then bent. General William Miller, the Englishman commanding 250 Hussars of Peru, had been ordered to outflank Canterac's right but had no time to execute - the Spanish were already among them. He had to charge frontally into the melee. Necochea was wounded and captured. Most of the patriot cavalry broke and fled in disorder. Bolivar himself, watching from a hill, turned back to hurry the infantry up to cover what was looking like total defeat. Major Braun's grenadiers had managed to break through the Spanish lines and were in an advantageous position, but they were nearly alone. The battle, as far as Canterac could see from his end, was won.

Lieutenant Colonel Isidoro Suarez was hidden behind a hill in the battlefield with the First Squadron of the Hussars of Peru. He had been waiting for orders. From his concealed position he could see the exposed left flank of the Spanish, who in chasing the broken patriot cavalry had lost their compact formation. He had no order to attack. Then Major Jose Andres Razuri rode up and gave him one - claiming it came from General La Mar, who had not actually given any such order. Suarez ordered the charge. The First Squadron came around the hill and struck the unguarded Spanish flank and rear simultaneously. The Spanish cavalry, sure they had won, were taken completely by surprise. Several minutes of butchery followed. The bulk of the patriot cavalry, seeing the situation flip, returned to the fight under General Miller, who had taken command after Necochea's capture. Colonel Silva managed to reorganize the Hussars of Colombia. The Spanish lost morale and broke.

When Canterac tried to understand what had happened, he could not. He told the Viceroy of Peru, Jose de la Serna e Hinojosa, in his report that he could find no explanation for the sudden disband of his cavalry. The Spanish lost over four hundred horses to the patriots, plus about two hundred fifty men. The patriots lost about one hundred fifty. The infantry of both armies had not yet reached the field. The whole engagement, fought entirely on horseback with cold steel, ran about forty-five minutes. After the battle, Razuri was reprimanded by General Jose de la Mar for inventing an order. La Mar told him: You should be executed, but today's victory is owed to you. Bolivar renamed the regiment that had turned the battle. The Hussars of Peru became the Hussars of Junin, the name they have carried ever since.

The defeat at Junin was not catastrophic in scale - the Spanish army was still intact, still in the field. But it broke morale, accelerated defections from royalist ranks, and forced Viceroy de la Serna himself to take direct command of his forces. Four months later, on 9 December 1824, the patriot army under Antonio Jose de Sucre met the royalists at Ayacucho. De la Serna was wounded and captured. Spain capitulated. Three centuries of continental Spanish empire in South America ended that day. The Battle of Junin in Argentine and Ecuadorian memory has produced poetry. Jose Joaquin de Olmedo of Guayaquil wrote a celebrated ode about it. Jorge Luis Borges, the great Argentine writer, wrote a poem about his ancestor Manuel Isidoro Suarez - the lieutenant colonel hidden behind the hill. Junin Lake itself, at 4,100 meters, sits today inside a national reserve, surrounded by the same wide, marshy pampa where the cavalry charge happened. The wind blows hard. The grass bends. The horses are gone.